The invention relates to an implantable stimulator for treating arrhythmic function disturbances of a heart, comprising: a stimulation electrode for transmitting stimulation pulses to the heart, the electrode being adapted to be disposed in one of the heart and the vicinity thereof, a pulse generator that is connected on an output side to the stimulation electrode for generating the stimulation pulses, a control unit that is connected on an output side to the pulse generator for controlling the pulse emission by the pulse generator, and a blood throughput device for controlling the pulse emission as a function of the cardiac pumping performance.
It is known to treat arrhythmic cardiac function disturbances, such as ventricular fibrillation, with the use of implantable cardioversion devices--also called defibrillators--that detect spontaneous cardiac signals, typically using an electrode disposed endocardially in the ventricle, and, when ventricular fibrillation or flutter is detected, transmit a high-energy current pulse--referred to hereinafter as defibrillation pulse--to the heart; the intensity of the pulse leads to a stimulation and depolarization of virtually all regions of the heart, so the arrhythmic state is ended and the normal sinus rhythm can reassume control of the heartbeat.
This type of identification of an arrhythmic cardiac state employing the evaluation of the intracardially-detected spontaneous cardiac signals is, however, susceptible to a wide range of possible interferences. For example, the amplitude of the spontaneous cardiac signals can be subjected to temporal fluctuations, e.g. in day/night rhythm, which impede reliable detection of arrhythmic cardiac states. It is also possible that electromagnetic interference signals are erroneously identified as intracardial EKG signals. Furthermore, the danger exists that spontaneous atrial cardiac signals electrically overspeak on the ventricle, so a relatively harmless atrial fibrillation is erroneously identified as ventricular fibrillation, and a defibrillation pulse is triggered, although the patient is not in a critical state. Thus, the reliability of the detection of arrhythmic cardiac states is unsatisfactory in the known defibrillators.
Cardiac pacemakers are also known for treating a disturbed stimulus transmission from the atrium to the ventricle. Pacemakers of this type usually detect spontaneous atrial actions using an electrode that is disposed endocardially in the atrium, and, following each spontaneous atrial action, respectively transmit a stimulation pulse to the ventricle with a delay of a predetermined AV transmission time. The delay of the ventricular stimulation after each atrial action is necessary to permit an optimum chamber filling prior to the contraction as a prerequisite for good cardiac pumping performance; the optimum value of the AV transmission time is individual to the respective pacemaker patient, and can also be susceptible to temporal fluctuations. Hence, a problem associated with the known pacemakers of this type is that the AV transmission time is not set optimally in most cases, leading to a reduction in the cardiac pumping performance.
It is therefore the object of the invention to provide an implantable stimulator in which the control of the pulse emission for ending arrhythmic disturbances in function is better adapted to the needs of the patient.